This invention relates to stable platform systems and, more particularly, to apparatus incorporated within a gimbal structure for isolating a payload platform, such as an initial stabilized platform, from linear laboratory motion without introducing a torque to the platform.
Platforms which are stabilized from rolling, pitching and yawing movements of a vehicle or other object, (including a person,) supporting the platform are employed for a variety of purposes. One such purpose is stabilizing a sighting device useful in the control of a vehicular camera, such as an optical or infrared camera or vidicon. Typically, the gyroscope, which may be a laser gyro, is mounted on the stabilized platform to sense rotational movements of the vehicle, the gyroscope being operative with a closed-loop stabilization system for supplying corrective torquing signals to actuators and/or drive motors for reorienting the platform by a known amount of angular increment in each of the three coordinates: roll, pitch and yaw.
It has been found that in the implementation of the stabilization system, the presence of linear, or translational, vibratory motion of the vehicle tends to limit the maximum accuracy which is obtainable for correction of the platform attitude in response to rotational movements of the vehicle. Attempts have been made to correct this situation by introducing shock mounts or resilient members within a gimbal structure supporting the platform. However, such vibration isolation apparatus may be off-centered relative to a plane containing a pivot axis of the gimbal structure so as to introduce an undesired torque from the translational movement, particularly a translational acceleration.
A further problem with vibration isolation apparatus occurs in the development of suitable actuators for torquing the platform in conjunction with operation of the isolation device, such as a shock absorber, spring, or other form of resilient material. In some cases, the actuators have been required to be excessively long to accommodate a stroke length of the vibration isolator, or have been required to have an excessively wide gap because of a requirement for operation across the isolation apparatus between the payload and a coarse support of the gimbal structure. Such constraints on the construction of the actuators produce actuators which are heavier than desired, and require more power than is desired. For example, a wide-gap electromagnetic actuator is less efficient than a narrow-gap electromagnetic actuator due to a lengthened flux path and requisite higher coil current to obtain the desired actuator movement.